Any communication network comprises of two fundamental parts, the nodes and the links. A node is some type of network device, such as a computer. Nodes are able to communicate with other nodes through links, like cables. Communication between nodes can be established by creating a closed circuit between two nodes in the network. However this technique does not utilize available capacity efficiently. Another technique that has become predominant in the field of communications, especially telecommunications is of packet-switched networks. Messages sent over a packet-switched network are first divided into packets containing the destination address. Then, each packet is sent over the network with every intermediate node and router in the network determining where the packet goes next. A packet does not need to be routed over the same links as previous related packets. Thus, packets sent between two network devices can be transmitted over different routes in the event of a link breakdown or node malfunction.
Packet switching dominates data networks like the internet. It provides an efficient way of data transfer. However, rapid increase in number of users of the Internet through mobile phones and other portable data devices has given rise to the problem of congestion of data lines. The demand for higher data rates has further aggravated the problem in the recent past. Code Division Multiple Access (CDMA) coding and protocol scheme has been quite successful in supporting the ever increasing cell-phone user capacity. The third generation (3G) wireless standards UMTS/IMT-2000 use the Wideband CDMA (WCDMA). This scheme supports high data rates and many data formats with different rates and qualities. The presence of more than one data format, however, results in a need to match the transfer data rate and data format to fit into CDMA channel. This is accomplished by using a technique known as rate matching.
Rate matching is a technique widely used in 3G wireless communication systems for adjusting the size of the data stream. In this technique, bits of an encoded block on a transport channel are repeated or punctured in order to match input data rate with the output data rate In cases where the input data rate is less than the fixed output data rate, certain input data bits are repeated. This is called ‘Repetition’. If the input data rate is more than the output data rate, certain data bits are punctured. This is known as ‘Puncturing’.
Whether a bit position is to be punctured or repeated, is determined by using eini, eplus and eminus. These are termed as RM Parameters. They are calculated according to the technical specification of 3rd Generation Partnership Project. (3GPP TS 25.212 v6.3.0), which is attached hereto as Appendix A.
eini: initial value of variable e in the rate matching pattern determination algorithm as given in 3GPP TS 25.212 v6.3.0 in the section 4.2.7.1. (in case of uplink) and section 4.2.7.2. (in case of downlink)
eplus: increment of variable e in the rate matching pattern determination algorithm as given in 3GPP TS 25.212 v6.3.0 in the section 4.2.7.1. (in case of uplink) and section 4.2.7.2. (in case of downlink)
eminus: decrement of variable e in the rate matching pattern determination algorithm as given in 3GPP TS 25.212 v6.3.0 in the section 4.2.7.1. (in case of uplink) and section 4.2.7.2. (in case of downlink)
The values of these parameters depend on ΔN where ΔN is number of bits to be punctured or repeated. ΔN is negative in case of puncturing and positive in case of repetition. Therefore the values of RM Parameters are different in case of puncturing and repetition.
In the conventional method of rate matching, input data bits are analyzed bit by bit. RM Parameters determine the status of each input data bit in the output data stream, which in turn determines the action to be taken on that bit. Possible actions can be puncture/repeat/no action. Since each bit is processed one at a time, the number of times each loop in the software module runs is large require more processing.
Therefore, there exists a need for a method and system employing a rate-matching algorithm that accomplishes the processes of repetition and puncturing in less number of steps and hence is faster.